Abstract: Because of the strong thermal accumulating effect, many kinds of defects were easily produced in aluminum alloy MIG (metal inert-gas)welding process.The intelligent closed-loop control system of the vision-based aluminum alloy MIG welding pool width was developed to solve this problem.The influences of welding pulse parameters on welding pool width were analyzed.The research shows that in order to obtain the ideal aluminum alloy MIG welding process, the control system must not only control the heat input but also remain the stabilization of welding process.The traditional single input and single output control system can' t satisfy this control requirement, so an intelligent controller based on Fuzzy controller and expert system (ES)was designed.The Fuzzy controller controls the heat input, while ES makes the welding parameters matching to remain the stabilization of welding process.The welding experiments show that the requirements for detecting and control of weld pool width could be satisfied by the established system.